// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/kernel/reboot.c
 *
 *  Copyright (C) 2013  Linus Torvalds
 */

#define pr_fmt(fmt) "reboot: " fmt

#include <linux/ctype.h>
#include <linux/export.h>
#include <linux/kexec.h>
#include <linux/kmod.h>
#include <linux/kmsg_dump.h>
#include <linux/reboot.h>
#include <linux/suspend.h>
#include <linux/syscalls.h>
#include <linux/syscore_ops.h>
#include <linux/uaccess.h>

/*
 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
 */

int C_A_D = 1;
struct pid *cad_pid;
EXPORT_SYMBOL(cad_pid);

#if defined(CONFIG_ARM)
#define DEFAULT_REBOOT_MODE = REBOOT_HARD
#else
#define DEFAULT_REBOOT_MODE
#endif
enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;

/*
 * This variable is used privately to keep track of whether or not
 * reboot_type is still set to its default value (i.e., reboot= hasn't
 * been set on the command line).  This is needed so that we can
 * suppress DMI scanning for reboot quirks.  Without it, it's
 * impossible to override a faulty reboot quirk without recompiling.
 */
int reboot_default = 1;
int reboot_cpu;
enum reboot_type reboot_type = BOOT_ACPI;
int reboot_force;

/*
 * If set, this is used for preparing the system to power off.
 */

void (*pm_power_off_prepare)(void);
EXPORT_SYMBOL_GPL(pm_power_off_prepare);

/**
 *    emergency_restart - reboot the system
 *
 *    Without shutting down any hardware or taking any locks
 *    reboot the system.  This is called when we know we are in
 *    trouble so this is our best effort to reboot.  This is
 *    safe to call in interrupt context.
 */
void emergency_restart(void)
{
    kmsg_dump(KMSG_DUMP_EMERG);
    machine_emergency_restart();
}
EXPORT_SYMBOL_GPL(emergency_restart);

void kernel_restart_prepare(char *cmd)
{
    blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
    system_state = SYSTEM_RESTART;
    usermodehelper_disable();
    device_shutdown();
}

/**
 *    register_reboot_notifier - Register function to be called at reboot time
 *    @nb: Info about notifier function to be called
 *
 *    Registers a function with the list of functions
 *    to be called at reboot time.
 *
 *    Currently always returns zero, as blocking_notifier_chain_register()
 *    always returns zero.
 */
int register_reboot_notifier(struct notifier_block *nb)
{
    return blocking_notifier_chain_register(&reboot_notifier_list, nb);
}
EXPORT_SYMBOL(register_reboot_notifier);

/**
 *    unregister_reboot_notifier - Unregister previously registered reboot notifier
 *    @nb: Hook to be unregistered
 *
 *    Unregisters a previously registered reboot
 *    notifier function.
 *
 *    Returns zero on success, or %-ENOENT on failure.
 */
int unregister_reboot_notifier(struct notifier_block *nb)
{
    return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
}
EXPORT_SYMBOL(unregister_reboot_notifier);

static void devm_unregister_reboot_notifier(struct device *dev, void *res)
{
    WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
}

int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
{
    struct notifier_block **rcnb;
    int ret;

    rcnb = devres_alloc(devm_unregister_reboot_notifier, sizeof(*rcnb), GFP_KERNEL);
    if (!rcnb) {
        return -ENOMEM;
    }

    ret = register_reboot_notifier(nb);
    if (!ret) {
        *rcnb = nb;
        devres_add(dev, rcnb);
    } else {
        devres_free(rcnb);
    }

    return ret;
}
EXPORT_SYMBOL(devm_register_reboot_notifier);

/*
 *    Notifier list for kernel code which wants to be called
 *    to restart the system.
 */
static ATOMIC_NOTIFIER_HEAD(restart_handler_list);

/**
 *    register_restart_handler - Register function to be called to reset
 *                   the system
 *    @nb: Info about handler function to be called
 *    @nb->priority:    Handler priority. Handlers should follow the
 *            following guidelines for setting priorities.
 *            0:    Restart handler of last resort,
 *                with limited restart capabilities
 *            128:    Default restart handler; use if no other
 *                restart handler is expected to be available,
 *                and/or if restart functionality is
 *                sufficient to restart the entire system
 *            255:    Highest priority restart handler, will
 *                preempt all other restart handlers
 *
 *    Registers a function with code to be called to restart the
 *    system.
 *
 *    Registered functions will be called from machine_restart as last
 *    step of the restart sequence (if the architecture specific
 *    machine_restart function calls do_kernel_restart - see below
 *    for details).
 *    Registered functions are expected to restart the system immediately.
 *    If more than one function is registered, the restart handler priority
 *    selects which function will be called first.
 *
 *    Restart handlers are expected to be registered from non-architecture
 *    code, typically from drivers. A typical use case would be a system
 *    where restart functionality is provided through a watchdog. Multiple
 *    restart handlers may exist; for example, one restart handler might
 *    restart the entire system, while another only restarts the CPU.
 *    In such cases, the restart handler which only restarts part of the
 *    hardware is expected to register with low priority to ensure that
 *    it only runs if no other means to restart the system is available.
 *
 *    Currently always returns zero, as atomic_notifier_chain_register()
 *    always returns zero.
 */
int register_restart_handler(struct notifier_block *nb)
{
    return atomic_notifier_chain_register(&restart_handler_list, nb);
}
EXPORT_SYMBOL(register_restart_handler);

/**
 *    unregister_restart_handler - Unregister previously registered
 *                     restart handler
 *    @nb: Hook to be unregistered
 *
 *    Unregisters a previously registered restart handler function.
 *
 *    Returns zero on success, or %-ENOENT on failure.
 */
int unregister_restart_handler(struct notifier_block *nb)
{
    return atomic_notifier_chain_unregister(&restart_handler_list, nb);
}
EXPORT_SYMBOL(unregister_restart_handler);

/**
 *    do_kernel_restart - Execute kernel restart handler call chain
 *
 *    Calls functions registered with register_restart_handler.
 *
 *    Expected to be called from machine_restart as last step of the restart
 *    sequence.
 *
 *    Restarts the system immediately if a restart handler function has been
 *    registered. Otherwise does nothing.
 */
void do_kernel_restart(char *cmd)
{
    atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
}

#ifdef CONFIG_NO_GKI
static ATOMIC_NOTIFIER_HEAD(pre_restart_handler_list);

int register_pre_restart_handler(struct notifier_block *nb)
{
    return atomic_notifier_chain_register(&pre_restart_handler_list, nb);
}
EXPORT_SYMBOL(register_pre_restart_handler);

int unregister_pre_restart_handler(struct notifier_block *nb)
{
    return atomic_notifier_chain_unregister(&pre_restart_handler_list, nb);
}
EXPORT_SYMBOL(unregister_pre_restart_handler);

void do_kernel_pre_restart(char *cmd)
{
    atomic_notifier_call_chain(&pre_restart_handler_list, reboot_mode, cmd);
}
#endif

void migrate_to_reboot_cpu(void)
{
    /* The boot cpu is always logical cpu 0 */
    int cpu = reboot_cpu;

    cpu_hotplug_disable();

    /* Make certain the cpu I'm about to reboot on is online */
    if (!cpu_online(cpu)) {
        cpu = cpumask_first(cpu_online_mask);
    }

    /* Prevent races with other tasks migrating this task */
    current->flags |= PF_NO_SETAFFINITY;

    /* Make certain I only run on the appropriate processor */
    set_cpus_allowed_ptr(current, cpumask_of(cpu));
}

/**
 *    kernel_restart - reboot the system
 *    @cmd: pointer to buffer containing command to execute for restart
 *        or %NULL
 *
 *    Shutdown everything and perform a clean reboot.
 *    This is not safe to call in interrupt context.
 */
void kernel_restart(char *cmd)
{
    kernel_restart_prepare(cmd);
    migrate_to_reboot_cpu();
    syscore_shutdown();
    if (!cmd) {
        pr_emerg("Restarting system\n");
    } else {
        pr_emerg("Restarting system with command '%s'\n", cmd);
    }
    kmsg_dump(KMSG_DUMP_SHUTDOWN);
    machine_restart(cmd);
}
EXPORT_SYMBOL_GPL(kernel_restart);

static void kernel_shutdown_prepare(enum system_states state)
{
    blocking_notifier_call_chain(&reboot_notifier_list, (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
    system_state = state;
    usermodehelper_disable();
    device_shutdown();
}
/**
 *    kernel_halt - halt the system
 *
 *    Shutdown everything and perform a clean system halt.
 */
void kernel_halt(void)
{
    kernel_shutdown_prepare(SYSTEM_HALT);
    migrate_to_reboot_cpu();
    syscore_shutdown();
    pr_emerg("System halted\n");
    kmsg_dump(KMSG_DUMP_SHUTDOWN);
    machine_halt();
}
EXPORT_SYMBOL_GPL(kernel_halt);

/**
 *    kernel_power_off - power_off the system
 *
 *    Shutdown everything and perform a clean system power_off.
 */
void kernel_power_off(void)
{
    kernel_shutdown_prepare(SYSTEM_POWER_OFF);
    if (pm_power_off_prepare) {
        pm_power_off_prepare();
    }
    migrate_to_reboot_cpu();
    syscore_shutdown();
    pr_emerg("Power down\n");
    kmsg_dump(KMSG_DUMP_SHUTDOWN);
    machine_power_off();
}
EXPORT_SYMBOL_GPL(kernel_power_off);

DEFINE_MUTEX(system_transition_mutex);

/*
 * Reboot system call: for obvious reasons only root may call it,
 * and even root needs to set up some magic numbers in the registers
 * so that some mistake won't make this reboot the whole machine.
 * You can also set the meaning of the ctrl-alt-del-key here.
 *
 * reboot doesn't sync: do that yourself before calling this.
 */
SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd, void __user *, arg)
{
    struct pid_namespace *pid_ns = task_active_pid_ns(current);
    char buffer[256];
    int ret = 0;

    /* We only trust the superuser with rebooting the system. */
    if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT)) {
        return -EPERM;
    }

    /* For safety, we require "magic" arguments. */
    if (magic1 != LINUX_REBOOT_MAGIC1 || (magic2 != LINUX_REBOOT_MAGIC2 && magic2 != LINUX_REBOOT_MAGIC2A &&
                                          magic2 != LINUX_REBOOT_MAGIC2B && magic2 != LINUX_REBOOT_MAGIC2C)) {
        return -EINVAL;
    }

    /*
     * If pid namespaces are enabled and the current task is in a child
     * pid_namespace, the command is handled by reboot_pid_ns() which will
     * call do_exit().
     */
    ret = reboot_pid_ns(pid_ns, cmd);
    if (ret) {
        return ret;
    }

    /* Instead of trying to make the power_off code look like
     * halt when pm_power_off is not set do it the easy way.
     */
    if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off) {
        cmd = LINUX_REBOOT_CMD_HALT;
    }

    mutex_lock(&system_transition_mutex);
    switch (cmd) {
        case LINUX_REBOOT_CMD_RESTART:
            kernel_restart(NULL);
            break;

        case LINUX_REBOOT_CMD_CAD_ON:
            C_A_D = 1;
            break;

        case LINUX_REBOOT_CMD_CAD_OFF:
            C_A_D = 0;
            break;

        case LINUX_REBOOT_CMD_HALT:
            kernel_halt();
            do_exit(0);
            panic("cannot halt");

        case LINUX_REBOOT_CMD_POWER_OFF:
            kernel_power_off();
            do_exit(0);
            break;

        case LINUX_REBOOT_CMD_RESTART2:
            ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
            if (ret < 0) {
                ret = -EFAULT;
                break;
            }
            buffer[sizeof(buffer) - 1] = '\0';

            kernel_restart(buffer);
            break;

#ifdef CONFIG_KEXEC_CORE
        case LINUX_REBOOT_CMD_KEXEC:
            ret = kernel_kexec();
            break;
#endif

#ifdef CONFIG_HIBERNATION
        case LINUX_REBOOT_CMD_SW_SUSPEND:
            ret = hibernate();
            break;
#endif

        default:
            ret = -EINVAL;
            break;
    }
    mutex_unlock(&system_transition_mutex);
    return ret;
}

static void deferred_cad(struct work_struct *dummy)
{
    kernel_restart(NULL);
}

/*
 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 * As it's called within an interrupt, it may NOT sync: the only choice
 * is whether to reboot at once, or just ignore the ctrl-alt-del.
 */
void ctrl_alt_del(void)
{
    static DECLARE_WORK(cad_work, deferred_cad);

    if (C_A_D) {
        schedule_work(&cad_work);
    } else {
        kill_cad_pid(SIGINT, 1);
    }
}

char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
static const char reboot_cmd[] = "/sbin/reboot";

static int run_cmd(const char *cmd)
{
    char **argv;
    static char *envp[] = {"HOME=/", "PATH=/sbin:/bin:/usr/sbin:/usr/bin", NULL};
    int ret;
    argv = argv_split(GFP_KERNEL, cmd, NULL);
    if (argv) {
        ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
        argv_free(argv);
    } else {
        ret = -ENOMEM;
    }

    return ret;
}

static int __orderly_reboot(void)
{
    int ret;

    ret = run_cmd(reboot_cmd);
    if (ret) {
        pr_warn("Failed to start orderly reboot: forcing the issue\n");
        emergency_sync();
        kernel_restart(NULL);
    }

    return ret;
}

static int __orderly_poweroff(bool force)
{
    int ret;

    ret = run_cmd(poweroff_cmd);
    if (ret && force) {
        pr_warn("Failed to start orderly shutdown: forcing the issue\n");

        /*
         * I guess this should try to kick off some daemon to sync and
         * poweroff asap.  Or not even bother syncing if we're doing an
         * emergency shutdown?
         */
        emergency_sync();
        kernel_power_off();
    }

    return ret;
}

static bool poweroff_force;

static void poweroff_work_func(struct work_struct *work)
{
    __orderly_poweroff(poweroff_force);
}

static DECLARE_WORK(poweroff_work, poweroff_work_func);

/**
 * orderly_poweroff - Trigger an orderly system poweroff
 * @force: force poweroff if command execution fails
 *
 * This may be called from any context to trigger a system shutdown.
 * If the orderly shutdown fails, it will force an immediate shutdown.
 */
void orderly_poweroff(bool force)
{
    if (force) { /* do not override the pending "true" */
        poweroff_force = true;
    }
    schedule_work(&poweroff_work);
}
EXPORT_SYMBOL_GPL(orderly_poweroff);

static void reboot_work_func(struct work_struct *work)
{
    __orderly_reboot();
}

static DECLARE_WORK(reboot_work, reboot_work_func);

/**
 * orderly_reboot - Trigger an orderly system reboot
 *
 * This may be called from any context to trigger a system reboot.
 * If the orderly reboot fails, it will force an immediate reboot.
 */
void orderly_reboot(void)
{
    schedule_work(&reboot_work);
}
EXPORT_SYMBOL_GPL(orderly_reboot);

static int __init reboot_setup(char *str)
{
    for (;;) {
        enum reboot_mode *mode;

        /*
         * Having anything passed on the command line via
         * reboot= will cause us to disable DMI checking
         * below.
         */
        reboot_default = 0;

        if (!strncmp(str, "panic_", 6)) {
            mode = &panic_reboot_mode;
            str += 6;
        } else {
            mode = &reboot_mode;
        }

        switch (*str) {
            case 'w':
                *mode = REBOOT_WARM;
                break;

            case 'c':
                *mode = REBOOT_COLD;
                break;

            case 'h':
                *mode = REBOOT_HARD;
                break;

            case 's':
                if (isdigit(*(str + 1))) {
                    reboot_cpu = simple_strtoul(str + 1, NULL, 0);
                } else if (str[1] == 'm' && str[2] == 'p' && isdigit(*(str + 3))) {
                    reboot_cpu = simple_strtoul(str + 3, NULL, 0);
                } else {
                    *mode = REBOOT_SOFT;
                }
                if (reboot_cpu >= num_possible_cpus()) {
                    pr_err("Ignoring the CPU number in reboot= option. "
                           "CPU %d exceeds possible cpu number %d\n",
                           reboot_cpu, num_possible_cpus());
                    reboot_cpu = 0;
                    break;
                }
                break;

            case 'g':
                *mode = REBOOT_GPIO;
                break;

            case 'b':
            case 'a':
            case 'k':
            case 't':
            case 'e':
            case 'p':
                reboot_type = *str;
                break;

            case 'f':
                reboot_force = 1;
                break;
        }

        str = strchr(str, ',');
        if (str) {
            str++;
        } else {
            break;
        }
    }
    return 1;
}
__setup("reboot=", reboot_setup);
